This invention relates to a retro-reflective sign particularly useful as a road sign which is made visible at night by reflecting automotive vehicle light beams.
Conventional highway signs, such as stop signs, one-way or wrong-way signs, informational type of signs such as indicating distances or highway exits and the like, are made of panels upon which the sign information or indicia is painted or otherwise imprinted. Such signs may also have standard recognized shapes which, themselves, indicate the type of message, such as a stop sign with an octagonal peripheral shape.
In order to make such signs more visible to vehicle drivers at night, it is conventional to make the signs reflective by utilizing special reflective paints or reflective coatings or beads. Thus, beams of light from the headlights of a vehicle are reflected from the sign panels, so that the messages or indicia are more readily visible to the vehicle driver as the vehicle approaches the sign. In order to make such sign messages visible at maximum distances, it is desirable to make the signs as reflective as possible. Thus, various techniques have been used to increase the reflectivity of the signs, so that their messages are brightly illuminated.
One known light reflective system involves the use of retro-reflective cube corner configurations impressed within the rear surface of a relatively transparent sign panel or lens panel. Incoming or incident light rays from an automotive vehicle light beam, which strike the exposed face of the panel, pass through the panel to the cube-corner retro-reflective configurations, located on the rear face of the panel, and are reflected back through the panel towards the source of the light. The light rays entering the cube corners are bounced from one surface to another and are reflected back approximately parallel to the corresponding incoming rays.
Examples of retro-reflective road signs are disclosed in U.S. Pat. No. 5,442,870 issued Aug. 22, 1995 to George E. Kochanowski for a "Reflective Sign." Other examples of the use of cube-corner, retro-reflective types of reflective signs or panels are disclosed in U.S. Pat. No. 2,167,149 to Walter F. Grote, issued Jul. 25, 1939 for a "Total Reflecting Prism Sheet"; U.S. Pat. No. 2,193,057 issued Mar. 12, 1940 to Horace N. Carver for a "Sign"; U.S. Pat. No. 3,772,810 issued Nov. 20, 1973 to Sam Kupperman, et al. for a "Reflecting Figure to be Applied to a Support Surface"; and U.S. Pat. No. 3,970,033 issued Jul. 20, 1976, to Henry Linder, et al. for a "Portable Reflector Device." Another use of such type of reflective device is illustrated in U.S. Pat. No. 3,409,344 issued Nov. 5, 1968 to Rudolf Douglas Balint for "Roadway Reflectors" used to mark the surfaces of pavements.
The prior retro-reflective signs, generally, reflect light by passage of the incoming or incident rays of light from an automotive vehicle headlight beam, through the front surface of a panel, then through the panel to the cube-corner reflective rear surface configurations. The light rays bounce between the three walls making up each cube corner and then are reflected back through the panel and out the front face in approximate parallelism to the incoming light rays. That is, corresponding incoming and outgoing light rays are roughly parallel.
It is desirable to direct the incoming rays as parallel as possible to the cube axes so that they reflect parallel to their respective cube axes. This provides for maximum intensity of reflection. There is a tendency for the reflected light rays to scatter or reflect at an angle relative to the driver of the vehicle which is the source of the incoming rays, rather than to be directed back toward the source of the light and the driver's view. This reduces the intensity of the reflection and correspondingly, the distance at which the reflected message on the sign may be clearly seen.
Thus, this present invention is concerned with improving the construction of the lens panel of a retro-reflective sign to better direct and intensify the reflected light. In general, this construction functions to initially bend and direct incoming light beams into approximate parallelism with the vertical axes of their respective cube-corner configurations and, then, to re-bend the reflected light coming from the cube corners towards the source of the light so as intensify the reflection and increase the distance at which the sign message is plainly visible.
In addition, this invention is concerned with improving the physical strength of a highway sign which is formed of molded plastic material and to make the sign message more visible to oncoming drivers by utilizing ambient light to backlight a sign message that may be molded or otherwise formed on the sign panel. That is, large sign panels which are formed of thin plastic sheet-like material are relatively weak. Since road signs are subject to intermittent relatively high forces, such as strong winds (which tend to damage the sign panels), this invention provides an integrally molded surface configuration on the sign panel and a separate support or backing panel which substantially rigidifies and strengthens the sign panel. Furthermore, the support panel may assist in utilizing ambient light to intensify the readability of the sign message.